Method for producing cases having rounded sides and being open at both ends

ABSTRACT

A method of producing metal cases having opposite rounded sides, preferably being of circular cylindrical shape, and being open at both ends, from a blank consisting of a rectangular piece of sheet metal, said method comprising the steps of I. bending each border of said blank to form a border zone of approximately the shape of a circular arch of an angle of between 75* and 120*, preferably about 90*, and having a radius of curvature smaller than, preferably between 20 and 40 percent smaller than the radius of curvature of the rounded side of the case to be provided by said border zones, II. bending the work obtained by step I at its middle line into U-shape with the two curved border zones facing each other and with the bottom of the U forming approximately a circular arch of an angle of between 125* and 175* and having a radius of curvature smaller than, preferably 20 to 40 percent smaller than the radius of the rounded side of the case to be provided at the middle zone of the blank, and III. arranging the U-shaped work thus obtained on a mandrel having the same cross-section as the case to be produced, but having dimensions so much smaller than the cross-section of the case as corresponding to slide fit, pressing said U-shaped work against said mandrel by means of two press dies having recesses together defining a cavity of the same shape and dimensions as the external sides of the case to be produced, one of said dies being forced towards the middle line of the work symmetrically thereto, the other being forced against the borders of the Ushaped work. This last said press die first being forced towards the mandrel until it has a minimal distance therefrom greater than the thickness of the original blank, then the first said of the two press dies is forced towards the mandrel until it has approximately the same distance therefrom as the second press die, whereupon both press dies are simultaneously forced together enclosing the case, therewith produced, and the mandrel, thereby a case being obtained having longitudinal edges directly contacting each other with a not unessential pressure and without the borders overlapping each other.

United States Patent Pedersen Sept. 26, 1972 [54] METHOD FOR PRODUCING CASES HAVING ROUNDED SIDES AND BEING OPEN AT BOTH ENDS [72] lnventor: Johannes Sigurd Pedersen, Aabyhoj,

Denmark [73] Assignee: Aarhus Metalemballage Industri, Aabyhoj, Denmark [22] Filed: May 26, 1970 [21] Appl. No.: 40,662

[30] Foreign Application Priority Data Primary Examiner-Lowell A. Larson Attorney-Ernest F. Marmorek [5 7] ABSTRACT A method of producing metal cases having opposite rounded sides, preferably being of circular cylindrical shape, and being open at both ends, from a blank consisting of a rectangular piece of sheet metal, said method comprising the steps of I. bending each border of said blank to form a border zone of approximately the shape of a circular arch of an angle of between 75 and preferably about 90, and having a radius of curvature smaller than, preferably between 20 and 40 percent smaller than the radius of curvature of the rounded side of the case to be provided by said border zones,

11. bending the work obtained by step 1 at its middle line into U-shape with the two curved border zones facing each other and with the bottom of the U forming approximately a circular arch of an angle of between and and having a radius of curvature smaller than, preferably 20 to 40 percent smaller than the radius of the rounded side of the case to be provided at the middle zone of the blank, and

III. arranging the U-shaped work thus obtained on a mandrel having the same cross-section as the case to be produced, but having dimensions so much smaller than the cross-section of the case as corresponding to slide fit, pressing said U-shaped work against said mandrel by means of two press dies having recesses together defining a cavity of the same shape and dimensions as the external sides of the case to be produced, one of said dies being forced towards the middle line of the work symmetrically thereto, the other being forced against the borders of the U-shaped work. This last said press die first being forced towards the ma dreliintflLhasafinima tanc ther f om greater, than the thickness of the original blank, then the first said of the two press dies is forced towards the mandrel until it has approximately the same distance therefrom as the second press die, whereupon both press dies are simultaneously forced together enclosing the case, therewith produced, and the mandrel, thereby a case being obtained having longitudinal edges directly contacting each other with a not unessential pressure and without the borders overlapping each other.

8 Claims, 9 Drawing Figures P'A'TENTEDSEPZS 1912 3.693; 398

o 0 F19 1 7 l0 {6 v 14 M Y /4 14 66 Fig. 2. Fig. 3. Fig.4.

"mm... Il -2 METHOD FOR PRODUCING CASES HAVING ROUNDEI) SIDES AND BEING OPEN AT BOTH ENDS formed by a zone of the blank on both sides of a middle line thereof, the other one of said rounded case sides having to be formed by the two borders of the blank parallel to said middle line.

In the production of metal cases from rectangular pieces of sheet-metal hitherto the adjoining edges of the work have been interconnected by welding. This involves, however, the development of a longitudinal bead, usually inside the case. In many cases, and particularly when the cases produced are of small dimensions, such as those used for small electric cells, and particularly when the cases are of circular cross section, or when the length of the cross section is only slightly larger than its width, such beads cannot be tolerated.

It has been proposed to produce such cases by drawing, so that the wall of the case is unabrupted, but this procedure has proved to be too expensive. Such drawn cases require a considerable number of finishing operations, partly to obtain the exact required length of the case, and partly to apply thereto the printings frequently required.

Onlyin a very few cases the case is required to be liquid-tight oi'airtight, and, therefore, ithas also been proposed to produce such cases by a bending-process.

The methods hitherto proposed for such a bendingprocess result therein, however,-that a gap is provided between the adjoining edges of the work, and this gap has such a width that it cannot be avoided that the cases, during transport or when passing a sorting and distributing drum, are pushed into one another, and that agglomerations result, which can be separated by hand only.

The object of the present invention is to provide a method as stated above, whereby it is possible to ensure such conditions that, in the case produced, the longitudinal free edges thereof are not only located exactly opposite to one another, but also are in contact and subjected to a certain compressive force, so that no gap remains between the adjoining, and contacting longitudinal edges, whereby it is effectively prevented that parts of other cases are pushed in between the edges.

According to the invention, this may be obtained thereby that I. the blank is by pressing bent along both borders for providing curved border Zones having in cross-section approximately the shape of a circular arc of an angle of between 75 and 120", preferably about 90, and having a radiusof curvature smaller than, preferably between 20 and 40 percent smaller than the final radius of the one of the one of the two rounded case sides to be formed by the two borders of the blank,

II. the work thus obtained is bent to a symmetrical U- shape along its middle line with the two arched border zones facing each other and with the bottom of the U at least approximately following a circular arc of an angle of between and and having a radius of curvature smaller than, preferably between 20 and 40 percent smaller than the radius of the one of the two rounded case sides to follow the middle line of the work, and

lll. the now U-shaped work is placed on a mandrel having a cross-section corresponding to the internal cross-section of the case to be produced, but having a dimension so much smaller than the same as corresponding to slide fit, whereupon the work is pressed between a first and a secondpress die, the recesses of which together define a cavity having dimensions corresponding to the external dimensions of the case to be produced and being adapted each to form the entirerounding of the case along a corresponding side thereof, thus in case the case to be produced has a circular crosssection, both said recesses being semi-cylindrical, said first die being adapted to act on the work sym metrically with respect to the middle line thereof, and said second die being adapted to act on the work symmetrically with respect to the curved border zones of the work, said second die being primarily pressed towards the mandrel, until the distance between theedges of its recess and the mandrel exceeds slightly the thickness of the work, whereupon said first die is pressed towards the mandrel, until its distance from the same is of the same. order of magnitude as is the distance of said second die from the mandrel, whereafter the said two dies are simultaneously pressed together enclosing the work and the mandrel;-

The result obtained hereby is probably due to the fact that the internal stresses produced in the plate material through the operations I and II, and tending to open the work, as a consequence of the increase of the radii of curvature of the curved zones provided by operation III, are not only relieved, but also replaced by new internal stresses which, in spite of the longitudinal edges of the work being only made contact one another without any overlapping, are sufficient to maintain intercontact of the edges under a relatively high pressure.

,This pressure becomes particularly high, when the case is of circular cross section, or when its oblongity is moderate, but it decreases with increasing length/width ratio of the cross section of the case, as a consequence of the resilience of the resulting flat side-parts of the case. The new method can, however, be effectively utilized for producing cases having flat side parts evenwhen, depending on the thickness of the plate, the cross sectional length/width ratio is higher than 3, and for production of cases of elliptical cross sections presenting still higher values of the said ratio.

In most cases it is further an advantage if one of the free ends of the case produced is immediately thereafter provided with a substantially U-shaped beading, whereby the case is becoming stronger, to such an extent that no risk will develop any longer that during transportation or handling it is deformed owing to lateral pressures, tending to displace the adjoining and contacting longitudinal edges from the position directly opposite to one another, which would involve overlapping of the borders, whereafter it would be difficult to re-condition such cases, and the cases might easily be subjected to further deformation.

With a view to the heading referred to, and to a subsequent, and usually likewise necessary, beading of the other end of the case, it may be appropriate that the rectangular blank used is bevel-cut, at least at the two corners of one end edge thereof, preferably at all four corners.

Other aspects, objects and the several advantagespf this invention will be apparent from a study of this disclosure, the accompamying drawings and the appended claims.

In the drawing FIG. 1 is an elavational view of a blank for use in connection with the method according to the invention,

FIGS. 2 and 3 are cross sectional views of the work subsequent to it having been subjected to a first and a second operation respectively,

FIG. 4 is an end view of a case produced by the method according to the invention, viewed towards the non-beaded end,

FIGS. 5 and 6 are together an elevational side view of a mandrel adapted for use in connection with the method according to the invention,

FIG. 7 is a top view of one end of the beading tool appearing in FIGS. 5 and 6,

FIG. 8 is a cross sectional view taken on line VIII- VIII in FIG. 5, and showing, moreover, a work positioned on the mandrel and twopress dies for the performance of the second operation, and,

FIG. 9 correspondingly a sectional view taken on line lX-IX in FIG. 5, and further showing press dies not shown in FIG. 5.

The blank 10 to be used for the new method is constituted by a rectangular piece of sheet-metal, as shown in FIG. 1. All corners of the blank 10 are bevel-cut as at 12. The blank 10 is first pressed between two press tools to provide curved borders 14, FIG. 2. The curvature of these borders 14 conforms approximately with a circular arc of an angle of 90 and having a radius of curvature that is 30 percent smaller than the radius of the circular cylindrical case 16 to be produced, FIG. 4.

The work 10 now obtained and provided with the curved edge parts 14 is then placed on the right part 18 of the mandrel 20, shown in FIGS. 5 and 6.

The mandrel part 18, having a length somewhat exceeding the length of the work 10, is supported by a foot 22, through which it is firmly held in position.

The mandrel part 18 has an upper surface 24 of semicircular shape and having a radius about 30 percent smaller than the radius of the case 16 to be produced, shown in FIG. 4. The semi-cylindrical surface 24 continues into parallel, vertical side walls 26 having a height approximately corresponding to US of the width of the blank 10, shown in FIG. 1. The mandrel part 18 is connected to the foot 22 by means of a connecting member 28, which is somewhat thinner than the mandrel part 18.

The top of the mandrel part 18 is provided with a longitudinal groove 30, adapted to receive sliding means for displacing the work along the mandrel 20.

When the work 10, FIG. 2, has been placed symmetrically over the mandrel part 18, it is pressed down over same by means of a press die 32, FIG. 8, having a length somewhat exceeding the length of the work 10, and provided with a recess 34, the bottom 36 of which having a cross-section formed as a circular arc of an angle of abt. and having a radius corresponding to the radius of the mandrel surface 24. The curved bottom 36 continues into outward bevelling plane side walls 38, forming between them an angle of abt. 30*, and each provided at the lower surface of the press die with a transition to this surface constituted by a curved portion 40.

When the work 10, shown in FIG. 2, has been pressed between the mandrel part 18 and the press die 32, it has been given the cross sectional shape shown in FIG. 3, being approximately U-shaped, with the curved bottom 42 of the U following the middle-line of the work, and having a radius of curvature approximately 30 percent smaller than the radius of the case to be produced, shown in FIG. 4. I

After the second pressing operation stated, the free edges of the curved borders 14 of the work will reach under the mandrel part 18 and have an interdistance slightly larger than the thickness of the connecting part 28. Thus, the work cannot be pulled vertically up from the mandrel, but is, pushed by means of sliding means, not shown, guided by the groove 30, displaced into the mandrel part 44, shown to the left in FIG. 5, and having a circular cross section with a radius corresponding to the radius of the case 16 to be produced, shown in FIG. 4, but being so much smaller than the latter as corresponding to slide fit. Thus the mandrel part 44 has a diameter exceeding the width of the mandrel part 18. The center axis of the mandrel part 44 is located in level with the bottom edge of the side-surfaces 26 of the mandrel part 18. Between the mandrel part 18 and the mandrel part 44, as shown in FIG. 5, there is a transitional part 46, securing a smooth transition between the outer surfaces of the mandrel part 18 and the connecting part 28 and the outer surface of the mandrel part 44. Therefore, when the work is displaced along the mandrel 20, from the mandrel part 18 unto the mandrel part 44, its curved borders 14 will be forced somewhat apartand engage the lower sides of the mandrel part 44, as will be apparent from FIG. 9, and will be retained in this position through the clamping effect thereby obtained.

The mandrel part 44 has a length slightly over double the length of the work 10, and the work is first moved from the mandrel part 18 onto the adjacent part of the mandrel part 44. On this part the work 10 is pressed between a lower die 48 and an upper die 50, having opposite recesses 52 and 54 respectively. Both these recesses 52 and 54 are of semi-cylindrical cross section with the same radius as the external radius of the case 16.

During the pressing operation the lower press die 48 is first forced upwards, until the upper edges of its recess 54 has a distance from the mandrel part 44 somewhat exceeding the thickness of the work 10, preferably being double this thickness. Thereafter the upper press die 50 is forced downwards towards the mandrel part 44. Thereby it is pressed against the longitudinal curved portion 42 of the work and forces the work downwards into the recess 54 of the lower press die alongside the walls thereof, whereby the curved borders 14 of the work are expanded to a certain extent, approaching one another at the same time. This displacement of thepress die 50 continues, until it reaches a position approximately symmetrical to the lower press die 48 relativ to a horizontal plane through the axis of the mandrel part 44, whereafter both press dies 48 and 50 are pressed symmetrically against one another. Thereby the work is given a cylindrical shape, and so that the edges of the curved borders 14 are in direct contact, exerting a not unessential pressure on one another. The press dies 48 and 50 are thereafter again moved apart, and by means of a movable gripper, not shown, the work is moved onto the outer portion of the mandrel part 44, shown in FIG. 6, where the work is allowed to rest during the pressing of the following work between the dies 48 and 50.

At the outer end of the mandrel part 44, by means of a stud 56, FIG. 6, a beading tool 58 is attached having over the greater part of its length the same diameter as has the mandrel part 44, but provided, adjacent thereto, with a circumferential groove 60. The length of the beading tool 58 outside the groove 60 is exactly equal to the length of the case to be produced. At its free end face the beading tool 58 is provided with a bead 62.

The case on the outer portion of the mandrel part 44, after a resting period corresponding to the pressing of a work on the inner portion of the mandrel part 44, is displaced fully onto the beading tool 58, and so that the end-edge thereof facing the mandrel part 44 is located at a small distance from the outer edge 64 of the groove 60. Thereafter a cheek, not shown, is brought to engage the groove 60 and is forced into close contactwith the edge 64. Thereafter a beading tool, known perse but not shown, is forced axially towards the case, which, when engaged by the tool, is displaced to the right in FIG. 6, until its inner end-edge contacts the cheek. The beading tool, thereafter, in co-operation with the beading bead 62, will produce a beading 66 at the outer endedge of the case, as appears from FIG. 4.

lclaim:

1. In the production of a metal case, having a first and a second rounded side opposite to each other, and being open at both ends, from a blank consisting of a rectangular piece of sheetmetal, said first rounded side to be formed by a zone of said blank on both sides of a middle line thereof, and second rounded side to be formed by the borders of the said blank parallel to said middle line; the method comprising the operations I. bending said blank by pressing along said borders for providing a first work having curved border zones, each in cross-section being approximately in the shape of a circular arc of an angle of between 75 and 120 and having a radius of curvature smaller than the radius of said second rounded side of said case to be produced,

II. bending said first work along said middle line to the shape of a symmetrical U, and with the two said curved border zones facing each other and with the bottom of the U approximately following a circular arc of an angle between 125 and 175 and having a radius of curvature smaller than the radius of said first rounded side of said case to be produced, a second U-shaped work being thereby provided,

Ill. placing said second U-shaped work on a mandrel having a cross-section corresponding to the internal cross-section of the said case to be produced but having dimensions so much smaller than said internal cross-section as to slide fit; pressing said .second U-shaped work when arranged on said mandrel between a first and a second press die each provided with a recess, said two recesses together defining a cavity having dimensions corresponding to the external dimensions of said case to be produced, each said recess further being adapted to form the entire rounding of one of said two rounded sides of said case, said first press die being adapted to act on said second U-formed I work symmetrically with respect to the said middle line thereof, said second press die being adapted to act on said second U-shaped work symmetrically with respect to the said two curved border zones thereof; forcing said second press die towards said mandrel until the distance between the edges of its said recess and the said mandrel exceed slightly the thickness of said blank; thereupon forcing said first press die towards said mandrel until its distance therefrom is of the same order of magnitude as is the distance of said second press die from said mandrel; and then forcing said two press dies simultaneously together enclosing said second work and said mandrel.

2. A method as defined in claim 1, each said border zone of said blank being given by said operation I a cross-section approximately in the shape of a circular arc of an angle of about 3. A method as defined in claim 1, each said border zone of said blank being given by said operation I a cross-section approximately in the shape of a circular are having a radius of curvature between 20 percent and 40 percent smaller than the radius of said second rounded side of said case to be produced.

4. A method as defined in claim 1, said bottom of said U formed by said first work by said operation [I being given approximately the shape of a circular are having a radius of curvature between 20 percent and 40 percent smaller than the radius of curvature of said first rounded side of said case to be produced.

5. A method as defined in claim 1 wherein each of said'borders has an end edge, further comprising the step of providing shortly after said operation III, one end edge of said case to be produced with a substantially U-shaped beading.

6. A method as defined in claim 5, said blank having the two corners of said rectangular piece of sheet-metal bevel-cut at one end thereof.

7. A method as defined in claim 2, in which a mandrel is used including a first mandrel part, a second mandrel part, a beading tool constituting an extension of said second mandrel part, a circumferential groove, adapted to receive a press cheek, being provided between said beading tool and said second mandrel part, said beading tool having a front face provided with an axially extending circumferential bead, said groove having a groove front edge at the side of said groove bordering said beading tool, said bead having a free front edge, the distance between said free front edge and said groove front edge being equal to the length of said case to be produced, said case formed on said second mandrel part having a rear edge, said case being displaced onto said beading tool until its rear edge is located in a distance outside said groove front edge, a press cheek being brought to engage said groove, forcing said press cheek against said groove front edge, forcing a beading die against said rear edge of said case for displacing the latter towards and for forcing it against said press cheek and in cooperation with said bead to provide said rear edge of said case with a U-shaped beading. U-shaped 8. In a method as defined in claim 5, by which for the performance of said operation III a mandrel is used having an extension constituting a beading tool, which beading tool is provided with a circumferential groove at the transition to said mandrel, which groove has a groove front edge at the side thereof bordering said beading tool, which further has a front face provided with an axially extending circumferential beading bead having a free front face, the distance between which and said groove front edge being exactly equal to the inner length desired of said case to be produced, the steps of displacing said case formed by said operation Ill from said mandrel onto said beading tool until its 

1. In the production of a metal case, having a first and a second rounded side opposite to each other, and being open at both ends, from a blank consisting of a rectangular piece of sheet-metal, said first rounded side to be formed by a zone of said blank on both sides of a middle line thereof, and second rounded side to be formed by the borders of the said blank parallel to said middle line; the method comprising the operations I. bending said blank by pressing along said borders for providing a first work having curved border zones, each in cross-section being approximately in the shape of a circular arc of an angle of between 75* and 120* and having a radius of curvature smaller than the radius of said second rounded side of said case to be produced, II. bending said first work along said middle line to the shape of a symmetrical U, and with the two said curved border zones facing each other and with the bottom of the U approximately following a circular arc of an angle between 125* and 175* and having a radius of curvature smaller than the radius of said first rounded side of said case to be produced, a second Ushaped work being thereby provided, III. placing said second U-shaped work on a mandrel having a cross-section corresponding to the internal cross-section of the said case to be produced but having dimensions so much smaller than said internal cross-section as to slide fit; pressing said second U-shaped work when arranged on said mandrel between a first and a second press die each provided with a recess, said two recesses together defining a cavity having dimensions corresponding to the external dimensions of said case to be produced, each said recess further being adapted to form the entire rounding of one of said two rounded sides of said case, said first press die being adapted to act on said second U-formed work symmetrically with respect to the said middle line thereof, said second press die being adapted to act on said second U-shaped work symmetrically with respect to the said two curved border zones thereof; forcing said second press die towards said mandrel until the distance between the edges of its said recess and the said mandRel exceed slightly the thickness of said blank; thereupon forcing said first press die towards said mandrel until its distance therefrom is of the same order of magnitude as is the distance of said second press die from said mandrel; and then forcing said two press dies simultaneously together enclosing said second work and said mandrel.
 2. A method as defined in claim 1, each said border zone of said blank being given by said operation I a cross-section approximately in the shape of a circular arc of an angle of about 90*.
 3. A method as defined in claim 1, each said border zone of said blank being given by said operation I a cross-section approximately in the shape of a circular arc having a radius of curvature between 20 percent and 40 percent smaller than the radius of said second rounded side of said case to be produced.
 4. A method as defined in claim 1, said bottom of said U formed by said first work by said operation II being given approximately the shape of a circular arc having a radius of curvature between 20 percent and 40 percent smaller than the radius of curvature of said first rounded side of said case to be produced.
 5. A method as defined in claim 1 wherein each of said borders has an end edge, further comprising the step of providing shortly after said operation III, one end edge of said case to be produced with a substantially U-shaped beading.
 6. A method as defined in claim 5, said blank having the two corners of said rectangular piece of sheet-metal bevel-cut at one end thereof.
 7. A method as defined in claim 2, in which a mandrel is used including a first mandrel part, a second mandrel part, a beading tool constituting an extension of said second mandrel part, a circumferential groove, adapted to receive a press cheek, being provided between said beading tool and said second mandrel part, said beading tool having a front face provided with an axially extending circumferential bead, said groove having a groove front edge at the side of said groove bordering said beading tool, said bead having a free front edge, the distance between said free front edge and said groove front edge being equal to the length of said case to be produced, said case formed on said second mandrel part having a rear edge, said case being displaced onto said beading tool until its rear edge is located in a distance outside said groove front edge, a press cheek being brought to engage said groove, forcing said press cheek against said groove front edge, forcing a beading die against said rear edge of said case for displacing the latter towards and for forcing it against said press cheek and in cooperation with said bead to provide said rear edge of said case with a U-shaped beading. U-shaped
 8. In a method as defined in claim 5, by which for the performance of said operation III a mandrel is used having an extension constituting a beading tool, which beading tool is provided with a circumferential groove at the transition to said mandrel, which groove has a groove front edge at the side thereof bordering said beading tool, which further has a front face provided with an axially extending circumferential beading bead having a free front face, the distance between which and said groove front edge being exactly equal to the inner length desired of said case to be produced, the steps of displacing said case formed by said operation III from said mandrel onto said beading tool until its rear edge is located in a distance in front of said groove front edge, bringing a press cheek to engage said groove, forcing said press cheek against said groove front edge, forcing a beading die against said end edge of said case for displacing the same towards and for forcing it against said press cheek and in cooperation with said bead to provide said end edge of said case with said beading. 